1. Technical Field
The present invention relates to a compound bearing apparatus suitable for the rotating portion of the so called precision mechanical equipment, and a spindle motor and a swing arm for hard disk drive means including such bearing apparatus.
2. Description of the Prior Art
A variety of structures of the bearing apparatus are known for the rotating portion of the precision mechanical equipment. In the case of the prior art as shown in FIG. 7, the compound bearing apparatus of one prior art includes a stepped shaft 41 having enlarged and reduced diameter shaft portions 41a, 41b, a sleeve outer race 42 surrounding the stepped shaft, and two rows of rotating bodies 44,45 interposed between the enlarged diameter shaft portion 41a and the sleeve outer race 42, and an inner race 43 fitted around the reduced diameter shaft portion 41b and the sleeve outer race 42 respectively.
In such compound bearing apparatus of the prior art, the clearance defined between the enlarged diameter shaft portion of the shaft and the sleeve outer race and that defined between the inner race and the sleeve outer race are closed by means of sealing plates 46,47 at the outer side of each of two rows of rotating bodies. This is effected for the purpose of preventing the lubricant presented around the balls 44,45, rolling recess 48a, 48b, 49a, 49b, and the retainer 50 from leaking out therefrom.
In the compound bearing apparatus of the prior art having above-mentioned structure, often caused is the shortage of the lubricant due to the dispersion thereof into the space A defined between two rows of balls 44, 45. This also causes the rotational noise or vibration and reduces the lifetime of the bearing apparatus.
When the spindle motor including such compound bearing apparatus of the prior art is used as a driving apparatus for a hard disk drive device, the lubricant dispersed by the high speed rotation of the bearing apparatus into the space A will transform into a mist of lubricant and produce a turbulence. This turbulence will produce noises or vibration to affect the stillness and the accuracy of the rotation of the motor.
Further, in the swing arm assembly employed as a swing arm for the hard disk drive device, it is necessary to displace the magnetic head accurately along the surface of the hard disk used as a magnetic storage medium by swinging the arm around the shaft accurately. Whereas the swing arm assembly including a compound bearing apparatus of the prior art is apt to produce rotational noises or vibrations due to the age deterioration of the compound bearing apparatus. These rotational noises or vibrations will often lead to a disk crash to impair the reliability of the hard disk drive means.
Accordingly, the object of the present invention is to provide a compound bearing apparatus having sealing means for preventing the lubricant presented around the rotating bodies from leaking out to the space defined between two rows of the rotating bodies as well as the out side of the bearing apparatus, and a spindle motor and a swing arm for hard disk drive means including such bearing apparatus.
These and other objects are achieved by a compound bearing apparatus in accordance with the first aspect of the present invention including a stepped shaft having an enlarged diameter shaft portion and reduced diameter shaft portion, a sleeve outer race surrounding the stepped shaft, and two rows of rotating bodies interposed therebetween, wherein:
the rotating bodies of the first row are disposed between an outer peripheral rolling recess formed directly on an outer peripheral surface of the enlarged diameter shaft portion and a first inner peripheral rolling recess formed directly on the inner peripheral surface of the sleeve outer race,
the rotating bodies of the second row are disposed between an outer peripheral rolling recess formed on an outer periphery of an inner race fitted over the reduced diameter shaft portion of said stepped shaft and a second inner peripheral rolling recess formed directly on the inner peripheral surface of the sleeve outer race,
an outer peripheral labyrinth recess formed on the outer peripheral surface of the enlarged diameter shaft portion at the longitudinal inner side of the rotating bodies of the first row,
a space defined between a shoulder, formed at a point of transition from the enlarged diameter shaft portion to the reduced diameter shaft portion, and an inner end of the inner race,
at the longitudinal outer side of the rotating bodies of the first row, a first outer sealing plate of ring shape having a central aperture is fixedly fitted at its outer periphery into an inner peripheral groove formed on the inner peripheral surface of the sleeve outer race,
the inner diameter of the central aperture is slightly larger than the enlarged diameter shaft portion to prevent the first outer sealing plate from contact with the stepped shaft and to provide a labyrinth seal function,
at the longitudinal outer side of the rotating bodies of the second row, a second outer sealing plate of ring shape having a central aperture is fixedly fitted at its outer periphery into an inner peripheral groove formed on the inner peripheral surface of the sleeve outer race,
the inner diameter of the central aperture is substantially equal to or smaller than the outer diameter of the inner race and larger than the outer diameter of the reduced diameter shaft portion to provide a labyrinth seal function,
at the longitudinal inner side of the rotating bodies of the first row, a first inner sealing plate of ring shape having a central aperture is fixedly fitted at its outer periphery into an inner peripheral groove formed on the inner peripheral surface of the sleeve outer race,
the inner diameter of the central aperture is substantially equal to or smaller than the outer diameter of the enlarged diameter shaft portion and larger than the outer diameter of the labyrinth recess to prevent the first inner sealing plate from contact with the stepped shaft to provide a labyrinth seal function,
at the longitudinal inner side of the rotating bodies of the second row, a second inner sealing plate of ring shape having a central aperture is fixedly fitted at its outer periphery into an inner peripheral groove formed on the inner peripheral surface of the sleeve outer race,
the inner diameter of the central aperture is substantially equal to or smaller than the outer diameter of the inner ring and larger than the outer diameter of the reduced diameter shaft portion of the stepped shaft to prevent the second inner sealing plate from contact with the stepped shaft or the inner race to provide a labyrinth seal function.
Further, a compound bearing apparatus in accordance with the second aspect of the present invention including a stepped shaft having enlarged diameter shaft portion and reduced diameter shaft portion, a sleeve outer race surrounding the stepped shaft, and two rows of rotating bodies interposed therebetween, wherein:
the rotating bodies of the first row are disposed between an outer peripheral rolling recess formed directly on an outer peripheral surface of the enlarged diameter shaft portion and a first inner peripheral rolling recess formed directly on the inner peripheral surface of the sleeve outer race,
the rotating bodies of the second row are disposed between an outer peripheral rolling recess formed on an outer periphery of an inner race fitted over the reduced diameter shaft portion of said stepped shaft and a second inner peripheral rolling recess formed directly on the inner peripheral surface of the sleeve outer race,
a space defined between a shoulder, formed at a point of transition from the enlarged diameter shaft portion to the reduced diameter shaft portion, and an inner end of the inner race,
at the longitudinal outer and inner side of the rotating bodies of the first row, a pair of first outer and inner sealing plates of ring shape having a central aperture respectively are fitted at their inner peripheries into a pair of peripheral grooves formed on each side of the peripheral rolling recess formed on the outer peripheral surface of the enlarged diameter shaft portion so as to be faced opposite to a pair of outer and inner peripheral grooves formed on each side of the first inner peripheral rolling recess of the sleeve outer race respectively,
the outer diameter of the central aperture is substantially equal to or larger than the inner diameter of the sleeve outer race and smaller than the outer diameter of the inner peripheral grooves respectively to prevent the first inner and second sealing plates from contact with the sleeve outer race to provide a labyrinth seal function,
at the longitudinal outer side of the rotating bodies of the second row, a second outer sealing plate of ring shape having a central aperture is fixedly fitted at its outer periphery into a peripheral groove formed on the outer side of the second inner peripheral rolling recess formed on the inner peripheral surface of the sleeve outer race so as to be faced opposite to an outer side of the inner race,
the inner diameter of the central aperture is substantially equal to or smaller than the outer diameter of the inner race and larger than the outer diameter of the reduced diameter shaft portion of the stepped shaft to prevent the second outer sealing plate from contact with the stepped shaft or the inner race to provide a labyrinth seal function,
at the longitudinal inner side of the rotating bodies of the second row, a second inner sealing plate of ring shape having a central aperture is fixedly fitted at its outer periphery into a peripheral groove formed on inner side of the second inner peripheral rolling recess formed on the inner peripheral surface of the sleeve outer race so as to be faced opposite to the space between the stepped shaft and the inner race,
the inner diameter of the central aperture is substantially equal to or smaller than the outer diameter of the inner race and larger than the outer diameter of the reduced diameter shaft portion of the stepped shaft to prevent the second inner sealing plate from contact with the stepped shaft or the inner race to provide a labyrinth seal function.
The spindle motor in accordance with the present invention includes a compound bearing apparatus of the structure of either of the above-mentioned structures. The rotor hub, the rotating member of the spindle motor is adapted to be journalled on the base by the compound bearing apparatus.
The swing arm in accordance with the present invention includes a compound bearing apparatus of the structure of either of the above-mentioned structures. The compound bearing apparatus is fitted within the cylindrical portion being the base of the swing arm to journal the swing arm rotatably.
The above-mentioned compound bearing apparatus is configured so that said outer peripheral labyrinth recess, said space defined between said shoulder and said inner end of the inner race, said first inner sealing plate and said second inner sealing plate cooperate to reduce dispersion of lubricant from said rolling bodies into a space between said two rows of rotating bodies.